This course is designed to cover subjects in advanced high school chemistry courses, correlating to the standard topics as established by the American Chemical Society. This course is a precursor to the Advanced Chemistry Coursera course. Areas that are covered include atomic structure, periodic trends, compounds, reactions and stoichiometry, bonding, and thermochemistry.

FV

Very clear in the explanations provided, it is a complete course to really introduce to basic concepts of chemistry such as stechiometry, thermodynamic, atom structures and reactions.

TM

Jun 21, 2017

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This is a great course! Very well explained! It's managing to keep my attention on 100% and that's not an easy task for anybody. Thank you for sharing your knowledge with us!

À partir de la leçon

Week 3

Now that we know the structure of an atom, we can explore how atoms combine to form either molecular or ionic compounds. Then we will learn the rules of nomenclature that ensure that a compound is named according to IUPAC rules. We will end this unit by looking at quantitative relationships for compounds including the molar mass of and mass percent of an element in a compound.

Enseigné par

Dr. Allison Soult

Lecturer

Dr. Kim Woodrum

Sr. Lecturer

Transcription

In this problem we want to find the mass percent of chromium in our aluminum dichromate. So here we're going to first find the molar mass of the aluminum dichromate. We see that we have two aluminum atoms, each with a mass of 26.98. So that gives us 53.96 from the aluminum. We have six chromium atoms, each with a molar mass of 52.00, which gives us a mass of 312. And we have 21 oxygen atoms. Remember that I have to take the 3 times 7 because I have 21 oxygens, each with a mass of 16, and that gives us a total of 336 for the oxygen. When I add all these values together, I end up with 701.96 grams per mole for the molar mass of aluminum dichromate. And then I want to find the percent of chromium. Remember that percent is always equal to part over the whole times 100. And so here I'm going to get my percent chromium, by looking at the mass from the chromium which is 312 divided by 701.96 times 100. And when I do that I find that the percent chromium equals 44.45%. If I did the same process for the aluminum and the oxygen, what I would find is that the 3 percentages sum, should sum to 100% total.